Many digital cameras currently have a zoom lens and a single image sensor, and capture a still image and a motion picture. Captured images are digitally processed to thus generate digital image files, which are stored in memory within a digital camera. A digital image file is then transferred to and displayed on a computer, or transferred to and printed by a printer.
A small size and a wide optical zoom range are desirable characteristics of a digital camera. A user prefers a wider zoom range to a limited zoom range. However, when a digital camera is provided with a wide zoom lens without sacrificing the quality of a captured image, the size of the digital camera is increased. An expensive camera, such as a single-lens reflex optical camera, enables use of a plurality of interchangeable lenses; for example, a 28-70 mm zoom lens and a 70-210 mm zoom lens. However, in the case of a compact camera, use of a plurality of interchangeable lenses poses inconvenience to the user.
Some digital cameras use a single lens or a plurality of image sensors to generate a single color mage. Light originating from a subject is split into a plurality of colors by means of a prism beam splitter. A plurality of monochrome image sensors are used for capturing RGB color images.
Japanese Patent Publication Laid-Open No. 2003-298919 describes that a small CCD having a high pixel density and a large CCD having a low pixel density are arranged for respective two optical systems.
Japanese Patent Publication Laid-Open No. 2002-314888 describes a configuration where a plurality of (three) image-capturing elements are provided in a single optical system. An attempt is made to enlarge an image-capturing range by means of setting view angle ranges of three image-capturing elements so as to differ from each other.
Japanese Patent Publication Laid-Open No. Hei-4-345378 describes a configuration where three CCDs are provided so as to be respectively assigned to three optical systems having different focal lengths; and where, by means of switching the CCDs, an image of a given focal length can be selectively acquired, or a plurality of images of different focal lengths can be simultaneously acquired.
However, in a configuration employing a plurality of optical systems, such as that described in Japanese Patent Publication Laid-Open No. 2003-298919 or Japanese Patent Publication Laid-Open No. Hei-4-345378, a parallax arises for reasons of differences in relative positions of a plurality of optical systems when the image of a single subject is captured, and hence there arises a necessity for compensation for a parallax or image processing taking into consideration a parallax. Meanwhile, in a configuration where a plurality of image-capturing elements are provided for a single optical system, such as that described in Japanese Patent Publication Laid-Open No. 2002-314888, such a problem of parallax does not arise. In Japanese Patent Publication Laid-Open No. 2002-314888, an attempt is made solely to enlarge an image-capturing range by means of simply making view angle ranges different from each other; and no consideration is paid to a more effective method of use, such as implementation of zooming action by use of a plurality of image-capturing elements, and the like. Moreover, in a case where a plurality of image-capturing elements are used, there is a risk of an increase in the degree of complication and size of the configuration and an increase in power consumption when compared with a configuration using a single image-capturing element. However, no consideration is paid to attainment of miniaturization and power-savings in a case where a plurality of image-capturing elements are used.